I wondered how much water that actually is. It’s less than 500,000 acre-feet per year, if we converted the entire USA. According to http://www.watereducation.org/photo-gallery/california-water-basics, one acre-foot meets the average water needs of 2 households. And just the State of California by itself gets 75 million acre-feet each year of fresh water in its waterways and aquifers.

In 2009 there were 117 million households in the USA. It appears this conversion would save less than 1% of household water usage. Converting the entire USA would save about 1/2 of 1% of the available annual freshwater just in California.